I have three table,
tblstock --> StockID(Primary Key),ProductCode,Status,
tblstockhistory --> StockID(tblstock table StockID, 1:N),Qty,invoceNo,MRP
tblstockinoutrtnstats --> StatsID,ProductCode,StockIN
Your going to want to use an ALTER TABLE query. Depending on what flavor of SQL you're using (SQLite, MySQL, PostgreSQL, etc.) the statement might look slightly different, but the basic command will be similar to
ALTER TABLE table_name ADD column_name data_type; (http://www.w3schools.com/sql/sql_alter.asp)
Without a Language:
All flavors of SQL I know of allow you to run SQL queries on the command line. Again, it will be slightly different depending on the flavor you're using.
If you're using postgres, type
psql <db_name> <username>
If you're using MySQL, type
mysql -U <username> <db_name>
If you're using another version of SQL, look at their help and/or man page to see what the exact syntax you need is for that specific flavor.